Method and system for automotive battery cooling

ABSTRACT

The present invention relates to a battery-cooling system. The battery-cooling system includes a battery array and a plurality of heat pipes. The heat pipes each include a low-profile extrusion having a plurality of hollow tubes formed therein. Each heat pipe includes an evaporator portion and a condenser portion. A heat-transfer fluid is disposed within the plurality of hollow tubes. The evaporator portion is disposed between successive batteries within the battery array. The condenser portion is disposed outside of the battery array and exposed to a heat sink.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-Part of U.S. patent applicationSer. No. 12/857,635, filed Aug. 17, 2010. U.S. patent application Ser.No. 12/857,635 is a Continuation of U.S. patent application Ser. No.10/998,199 (now U.S. Pat. No. 7,857,037), filed Nov. 26, 2004. U.S.patent application Ser. No. 10/998,199 is a Continuation-in-Part of U.S.patent application Ser. No. 10/305,662 (now U.S. Pat. No. 6,834,712),filed Nov. 26, 2002. U.S. patent application Ser. No. 10/305,662 claimspriority to U.S. Provisional Patent Application No. 60/334,235 filedNov. 27, 2001. This application claims priority to U.S. ProvisionalPatent Application No. 61/412,817, filed Nov. 12, 2010. U.S. patentapplication Ser. No. 12/857,635, U.S. patent application Ser. No.10/998,199, U.S. patent application Ser. No. 10/305,662, U.S. patentapplication Ser. No. 12/871,583, U.S. patent application Ser. No.11/336,698, U.S. patent application Ser. No. 10/328,537, U.S. patentapplication Ser. No. 09/328,183, U.S. patent application Ser. No.08/327,329, U.S. Provisional Patent Application No. 60/525,242, U.S.Provisional Patent Application No. 60/334, 235, U.S. Provisional PatentApplication No. 61/412,817, and U.S. Provisional Patent Application No.60/088,428 are each incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The present application relates generally to battery cooling systems andmore particularly, but not by way of limitation, to battery coolingsystems incorporating heat pipes constructed with low-profile extrusionsadapted for select heat exchange and designed for use with a batteryarray.

2. History of the Related Art

Dependence on non-renewable carbon-based energy sources, such as, forexample, oil, gas, coal, and the like has led to intense focus ondevelopment of alternative energy sources. Moreover, detrimentalenvironmental effects believed to be associated with carbon-based fuelshave contributed to an urgency with which alternative energy sources aredeveloped. Chief among alternative energy initiatives is development ofalternatively-fueled vehicles. In the United States alone, eachpassenger vehicle is estimated to release in excess of approximately11,000 pounds of carbon dioxide along with smaller amounts of variousother pollutants. Pollution worsens air quality and, in many cases,leads to respiratory problems. In addition, carbon-based pollutants arecommonly believed to be a contributing factor in climate change andglobal warming.

The last decade has seen progress in development of alternatively-fueledvehicles. Vehicles fueled by, for example, natural gas, present cleanerand cheaper alternatives to traditional gasoline-powered vehicles. Inaddition, hybrid vehicles, combining a small gasoline-powered enginewith a battery backup, have been developed. While these developmentscertainly amount to improvements in existing technology, the long-termgoal of automotive research and development is development of aneconomical electric-powered vehicle.

Development of electric-powered vehicles present unique challenges toauto manufacturers. For example, electric-powered vehicles typicallyrequire a potential difference of approximately 36 to approximately 48Volts. Most commercially-available electric-powered vehicles generatethe required voltage with a large battery array. Such an array caninclude, for example, between six and nine 12-Volt batteries. Therequirement of a large battery array presents a number of designchallenges. First, a battery array generates considerable heat that mustbe dissipated to a heat sink. Second, a battery array must beefficiently sized to fit within space-confined areas of a passengervehicle. Consequently, any cooling system for the battery array mustalso be economically sized.

SUMMARY

The present invention relates generally to battery-cooling systems. Inone aspect, the present invention relates to a battery-cooling system.The battery-cooling system includes a battery array and a plurality ofheat pipes. Each heat pipe includes a low-profile extrusion having aplurality of hollow tubes formed therein. Each heat pipe includes anevaporator portion and a condenser portion. A heat-transfer fluid isdisposed within the plurality of hollow tubes. The evaporator portion isdisposed between successive batteries within the battery array. Thecondenser portion is disposed outside of the battery array and exposedto a heat sink.

In another aspect, the present invention relates to a method of coolinga battery array. The method includes providing a plurality of heatpipes. Each heat pipe includes a low-profile extrusion having aplurality of hollow tubes formed therein. Each heat pipe includes anevaporator portion and a condenser portion. The method further includesplacing the evaporator portion between successive batteries within thebattery array and arranging the evaporator portion to maximize thermalexposure of the evaporator portion to the successive batteries. Themethod further includes conducting heat into the evaporator portion fromthe battery array and discharging the heat from the condenser portion toa heat sink.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and forfurther objects and advantages thereof, reference may now be had to thefollowing description taken in conjunction with the accompanyingdrawings in which:

FIG. 1 is a perspective view of a battery-cooling system according to anexemplary embodiment;

FIG. 2A is a cross-sectional view, taken about section line A-A, of thebattery-cooling system of FIG. 1 according to an exemplary embodiment;

FIG. 2B is a heat-transfer diagram of a battery-cooling system accordingto an exemplary embodiment;

FIG. 3 is a perspective view of a heat pipe according to an exemplaryembodiment;

FIG. 4 is a perspective view of a battery-cooling system according to anexemplary embodiment; and

FIG. 5 is a flow diagram of a process for cooling a battery arrayaccording to an exemplary embodiment.

DETAILED DESCRIPTION

Various embodiments of the present invention will now be described morefully with reference to the accompanying drawings. The invention may,however, be embodied in many different forms and should not be construedas limited to the embodiments set forth herein.

As used herein, the term “low-profile extrusion” refers to aheat-exchange apparatus including an integral piece of metal having aplurality of hollow tubes formed therein containing a heat-transferfluid. In one embodiment, the low-profile extrusion includes multi-voidmicro-extruded hollow tubes designed to resist corrosion and to operateunder pressures and temperatures required by modern environmentally-saferefrigeration gases.

In a typical embodiment, the plurality of hollow tubes areinterconnected at their ends so as to allow fluid communication betweeneach tube. Low-profile extrusions are typically formed fromheat-conductive materials such as, for example, aluminum. In variousalternative embodiments, other heat-conductive materials such as, forexample, copper, steel, and other metals or metal alloys may be used. Ina typical embodiment, the plurality of hollow tubes have a diameter in arange of about 0.0625 inches to about 0.5 inches, but, in variousalternative embodiments, the plurality of hollow tubes may also havesignificantly smaller diameters.

Low-profile extrusions are typically manufactured with a profile, orheight, as low as about 0.05 inches and with the plurality of hollowtubes having varying inner diameters. Future advances may allowlow-profile extrusions to be manufactured with smaller profiles.Low-profile extrusions have been used in heat-exchanger applications inthe automotive industry and are commercially available in strip form(having a generally rectangular geometry) or coil form (a continuousstrip coiled for efficient transport). More detailed disclosure ofexemplary low-profile extrusions may be found in U.S. Pat. No.6,935,409, filed Jun. 8, 1999, U.S. Pat. No. 6,988,315, filed Dec. 23,2002, and U.S. Pat. No. 7,802,436, filed Jan. 20, 2006 each of which isincorporated herein by reference.

FIG. 1 is a perspective view of a battery-cooling system according to anexemplary embodiment. A battery-cooling system 100 includes a batteryarray 10 having a plurality of batteries 12 and a plurality of heatpipes 14. For exemplary purposes, the battery array 10 is illustrated asbeing a 3×3 array; however, one skilled in the art will recognize thatany size array could be utilized. In a typical embodiment, the pluralityof batteries 12 may be, for example, 12-Volt Lithium-ion batteries orany other type of battery. In the embodiment shown in FIG. 1, thebattery array 10 is structured such that the plurality of batteries 12are arranged into rows 20 and columns 22. In a typical embodiment, theplurality of heat pipes 14 include low-profile extrusions as describedhereinabove.

Still referring to FIG. 1, each heat pipe of the plurality of heat pipes14 includes an evaporator portion 16 and a condenser portion 18. Theevaporator portion 16 is disposed between adjacent batteries of theplurality of batteries 12. In an exemplary embodiment, the evaporatorportion 16 is disposed between successive rows 20 of the plurality ofbatteries 12. In the embodiment shown in FIG. 1, the plurality of heatpipes 14 are arranged in an angular pattern between the rows 20. Thecondenser portion 18 of the plurality of heat pipes 14 extends beyondthe battery array 10 and is thermally exposed to a heat sink 210 (shownin FIG. 2B). Extension of the condenser portion 18 beyond the batteryarray 10 allows discharge of heat from the battery array 10. Asillustrated in FIG. 1, in various embodiments, the plurality of heatpipes 14 may be arranged to span a distance between a lower left corner11 of a left-most battery of the plurality of batteries 12 and an upperright corner 13 of a right-most battery of the plurality of batteries12. Angular arrangement of the plurality of heat pipes 14 providesseveral advantages during operation of the battery-cooling system 100.First, angular arrangement of the plurality of heat pipes 14 allowsincreased surface contact between the evaporator portion 16 and theplurality of batteries 12 thereby maximizing thermal exposure betweenthe plurality of batteries 12 and the evaporator portion 16. Second,angular placement of the plurality of heat pipes 14 allows condensedheat-transfer fluid within the plurality of heat pipes 14 to move fromthe condenser portion 18 to the evaporator portion 16 via gravitythereby eliminating need for a pump. An exemplary heat pipe 14 is thePhaseplane° manufactured and distributed by Thermotek, Inc.

FIG. 2A is a cross-sectional view, taken about section line A-A, of thebattery-cooling system of FIG. 1 according to an exemplary embodiment.In FIG. 2A, the plurality of batteries 12 are shown arranged in rows 20.The plurality of heat pipes 14 are shown with the evaporator portion 16disposed between successive rows 20 and arranged in an angular pattern.The condenser portion 18 of the heat pipe is shown extending beyond thebattery array 10. Extension of the condenser portion 18 beyond thebattery array 10 allows discharge of heat from the battery array 10.

FIG. 2B is a heat-transfer diagram of the battery-cooling system of FIG.1 according to an exemplary embodiment. A heat pipe of the plurality ofheat pipes 14 is shown disposed between adjacent batteries of theplurality of batteries 12. During operation, heat 202 is generated bythe plurality of batteries 12. The heat 202 is conducted into theevaporator portion 16 of the plurality of heat pipes 14 and causesvaporization of a heat-transfer fluid 204 contained in the plurality ofheat pipes 14. Heat-transfer fluid vapor migrates to the condenserportion 18 as illustrated by arrow 212. The condenser portion 18 isthermally exposed to a heat sink 210. In various embodiments, the heatsink 210 may be, for example, an exterior environment, a vehicle frame,or a secondary cooling circuit. The heat transfer fluid vapor condensesin the condenser portion 18 thus discharging heat 208 to the heat sink210.

FIG. 3 is a perspective view of a heat pipe according to an exemplaryembodiment. The plurality of heat pipes 14 comprise a low-profileextrusion 42. The low-profile extrusion 42 includes a plurality ofhollow tubes 41 formed therein. In various embodiments, the low-profileextrusion 42 includes a wick structure (not explicitly shown) inside theplurality of hollow tubes 41. In various embodiments, the wick structuremay include, for example, internal fins, grooved inner side walls, ormetal screens, so as to maximize heat transfer capability via capillaryaction.

Still referring to FIG. 3, to form the plurality of heat pipes 14, theplurality of hollow tubes 41 are evacuated. After evacuation, the hollowtubes 41 are charged with a heat-transfer fluid such as, for example,water, glycol, alcohol, or other conventional refrigerant. Aftercharging, ends 41 a and 41 b of the plurality of hollow tubes 41 aresealed. The plurality of heat pipes 14 generally has an effectivethermal conductivity several multiples higher than that of a solid rod.This increase in efficiency is due to the fact that phase-change heattransfer coefficients are high compared to thermal conductivity ofconventional materials.

Still referring to FIG. 3, the low-profile extrusion 42 is formed intothe evaporator portion 16, for contacting heat-generating componentssuch as, for example, the plurality of batteries 12, and the condenserportion 18. The condenser portion 18 is illustrated by way of example inFIG. 3 as being placed at an angle relative to the evaporator portion16; however, one skilled in the art will recognize that, in variousembodiments, the evaporator portion 16 and the condenser portion 18 maybe co-planar.

Referring to FIGS. 1-3, during operation, heat 202 generated by theplurality of batteries 12 is transferred to the heat-transfer fluid 204in the evaporator portion 16. Heat 202 causes the heat-transfer fluid204 in the evaporator portion 16 to vaporize within the plurality ofhollow tubes 41. The resulting heat-transfer fluid vapor is less densethan surrounding liquid. Thus, the heat-transfer fluid vapor riseswithin the plurality of hollow tubes 41 into the condenser portion 18.The heat-transfer fluid 204 that is in the liquid phase may also betransferred from the evaporator portion 16 to the condenser portion 18via capillary action of the wick structures (not explicitly shown). Inthe condenser portion 18, the heat-transfer fluid vapor condenses into aliquid onto the inner walls of the plurality of hollow tubes 41. Theheat 208 released by condensation of the heat-transfer fluid vapor isdischarged to the heat sink 210. In an exemplary embodiment, the heat208 may be transferred to an exterior environment via, for example, airflow 48.

Still referring to FIGS. 1-3, in various embodiments, transfer of theheat 208 to the heat sink 210 can be facilitated utilizing a fan (notexplicitly shown) to increase the air flow 48. Further, in variousembodiments, at least one fin (not explicitly shown) may be attached tothe condenser portion 18 to facilitate transfer of the heat 208 from thecondenser portion 18 to the heat sink 210. In other embodiments, athermoelectric element (not explicitly shown) may be used to facilitatetransfer of the heat 208 to the heat sink 210. An exemplarythermoelectric element is shown and described in U.S. patent applicationSer. No. 08/327,329 (now U.S. Pat. No. 5,561,981, filed Sep. 16, 1994and incorporated herein by reference. In still other embodiments, acooling circuit (not explicitly shown), containing a secondheat-transfer fluid (not explicitly shown), may be used to transfer theheat 208 from the condenser portion 18 to the heat sink 210. Finally, invarious embodiments, a frame of a vehicle (not explicitly shown) may beused as the heat sink 210.

FIG. 4 is a perspective view of a battery-cooling system according to anexemplary embodiment. In a typical embodiment, a battery-cooing system400 includes a battery array 404 having a plurality of batteries 407arranged in a plurality of rows 409 and a plurality of columns 410. Atleast one heat pipe 402 is disposed in gaps between successive batteriesof the plurality of batteries 407. The at least one heat pipe 402includes an evaporator portion 403 and a condenser portion 406. Theevaporator portion 403 of the at least one heat pipe 402 is disposedbetween successive batteries 407 within the battery array 404. The atleast one heat pipe 402 is depicted by way of example in FIG. 4 as beingdisposed between successive rows of the plurality of rows 409 andsuccessive columns of the plurality of columns 410; however, one skilledin the art will recognize that the at least one heat pipe 402 may bearranged in any appropriate fashion within the battery array 404. Thecondenser portion 406 extends above the plurality of batteries 407.

Still referring to FIG. 4, the at least one heat pipe 402 is orientedvertically with respect to the battery array 10. During operation, heatis conducted from the plurality of batteries 407 into the evaporatorportion 403 thereby causing a heat-transfer fluid (not explicitly shown)to vaporize as described above with respect to FIG. 3. In a typicalembodiment, resulting heat-transfer fluid vapor rises within the atleast one heat pipe 402 to the condenser portion 406. In the condenserportion 406, the heat-transfer vapor condenses into a liquid and heat isreleased to the environment via, for example, air flow 408.

FIG. 5 is a flow diagram of a process for cooling a battery arrayaccording to an exemplary embodiment. A process 500 begins at step 502.At step 504, a heat pipe 14 is placed between successive batteries 12 ofa battery array 10. At step 506, the heat pipe 14 is arranged tomaximize thermal exposure of the heat pipe 14 to the battery array 10.At step 508, heat is conducted into an evaporator portion 16 of the heatpipe 14 from the battery array 10. At step 510, the heat is dischargedto an exterior environment from the condenser portion 18 of the heatpipe 14. The process 500 ends at step 512.

Although various embodiments of the method and system of the presentinvention have been illustrated in the accompanying Drawings anddescribed in the foregoing Specification, it will be understood that theinvention is not limited to the embodiments disclosed, but is capable ofnumerous rearrangements, modifications, and substitutions withoutdeparting from the spirit and scope of the invention as set forthherein. For example, the heat pipes 14 and 402 have been shown anddescribed herein as having a generally flat profile; however, oneskilled in the art will recognize that the heat pipes 14 and 402 couldhave any profile shape such as, for example, round. It is intended thatthe Specification and examples be considered as illustrative only.

1. A battery-cooling system comprising: a battery array; a plurality ofheat pipes, each heat pipe of the plurality of heat pipes comprising alow-profile extrusion having a plurality of hollow tubes formed therein,each heat pipe of the plurality of heat pipes comprising an evaporatorportion and a condenser portion; a heat-transfer fluid disposed withinthe plurality of hollow tubes; wherein the evaporator portion isdisposed between successive batteries within the battery array; andwherein the condenser portion is disposed outside the battery array andexposed to a heat sink.
 2. The battery-cooling system of claim 1,wherein the evaporator portion is arranged at an angle relative to thebattery array.
 3. The battery-cooling system of claim 1, wherein thebattery array comprises a plurality of batteries arranged in a pluralityof rows and a plurality of columns.
 4. The battery-cooling system ofclaim 3, wherein each heat pipe of the plurality of heat pipes isdisposed between successive rows of the plurality of rows.
 5. Thebattery-cooling system of claim 3, wherein each heat pipe of theplurality of heat pipes is disposed between successive columns of theplurality of columns.
 6. The battery-cooling system of claim 1, whereineach battery of the battery array are Lithium-ion batteries.
 7. Thebattery-cooling system of claim 1, further comprising a plurality offins coupled to the condenser portion.
 8. The battery-cooling system ofclaim 1, further comprising a cooling circuit thermally exposed to thecondenser portion.
 9. The battery-cooling system of claim 8, wherein thecooling circuit comprising a second heat-transfer fluid therein.
 10. Thebattery-cooling system of claim 1, wherein the condenser portion isthermally exposed to a frame of a vehicle.
 11. A method of cooling abattery array, the method comprising: providing a plurality of heatpipes, each heat pipe of the plurality of heat pipes comprising alow-profile extrusion having a plurality of hollow tubes formed therein,each heat pipe of the plurality of heat pipes comprising an evaporatorportion and a condenser portion; placing the evaporator portion betweensuccessive batteries within the battery array; arranging each heat pipeof the plurality of heat pipes to maximize thermal exposure of theevaporator portion to the successive batteries; conducting heat into theevaporator portion from the battery array; and discharging the heat fromthe condenser portion to a heat sink.
 12. The method of claim 11,wherein the arranging comprises placing the evaporator portion at anangle relative to the battery array.
 13. The method of claim 11, whereinthe discharging comprises discharging the heat to a frame of a vehicle.14. The method of claim 11, wherein the discharging comprises removingthe heat via a cooling circuit.
 15. The method of claim 14, wherein thecooling circuit comprises a second heat-transfer fluid therein.